Natural enrichment of nickel and vanadium in sediment cores near oil extraction sites in the Gulf of Mexico

The coastal area of Veracruz state is located next to the oil extraction area of the Gulf of Mexico. Elements as Ni and V can be indicators of activities of oil extraction. In order to evaluate the contribution of Ni and V related to petroleum activities two sediment cores (Ll-1, Ll-2), from the El Llano lagoon in Veracruz. Moreover, major (Al, Ca, Fe) and trace elements (Co, Li, Mn, Sr and Zn) content was also analyzed with inductively coupled plasma mass spectroscopy (Icp-Ms). Complementary, grain size (with laser diffraction) and organic carbon (with elemental analyzer) were analyzed. The grain size results showed predominantly sandy sediments in both cores and relatively low (<3 %) organic carbon results. Average concentrations of Ni and V were higher than the continental crust average. Normalized enrichment factors reached moderately enriched levels for Ni (Nef = 4) and significantly enrichment for V (Nef = 6) in both cores. The Ni/V ratio indicated enrichment of V and different origin of both elements. Nickel was associated with Al, Fe, Co, Li and Zn. On the contrary, W was not associated with those elements; it had cyclic increments since the deep sections to the surface probably associated to sporadic releases of natural bituminous oil seeps. (author)